Electro-hydraulic shock wave systems have been used to disintegrate kidney and urethral stones by applying focused shock waves to the stone. A few hundred up to a few thousand shock waves may be required to break a stone within a mammal into small pieces of 3-4 mm diameter which are able to pass over a period of several weeks through the urethra and the bladder out of the patient's body.
Devices using electro-hydraulic (U.S. Pat. No. 4,539,989), piezoceramic (U.S. Pat. No. 5,119,801) or electromagnetic (U.S. Pat. No. 5,174,280) shock wave or pressure pulse generating elements have been described.
The patents used herein to illustrate the invention and, in particular, to provide additional details respecting the practice are incorporated herein by reference in their entirety.
In certain of non-urological applications, shock waves and pressure pulses may be used to treat/cure orthopedic painful conditions. The treated indications may be related to tendons, ligaments, soft tissue and include muscle pain and calcification in tissue. Suitable devices and procedures have been described (U.S. Pat. No. 5,545,124 and U.S. Pat. No. 5,595,178). Certain unfocused waves have been described in, for example, United States Patent Application 20040162508. The treatment of tissue with shock waves has also been discussed (United States Patent Application 20040162508).
Known devices generally make use of more or less strong focused shock waves which are focused by ellipsoidal reflectors in electro-hydraulic devices (U.S. Pat. No. 4,539,989) or by parabolic reflectors in devices using electromagnetic sources which are emitting waves from a cylindrical surface (U.S. Pat. No. 5,174,280). Other electromagnetic sources may make use of acoustic lenses of different shapes, for example, concave or convex, depending on the sound velocity and density of the lens material used (U.S. Pat. No. 5,419,335 and European Patent 1 445 758 A2). Piezoelectric sources often use spherical surfaces to emit acoustic pressure waves which are self focused to the center of the sphere (U.S. Pat. No. 5,222,484). The same type of focusing has been used in spherical electromagnetic devices (U.S. Pat. No. 4,807,627).
In certain non-urological applications, focused shock waves are used to treat ischemic heart tissue for generating better blood supply by targeting the treated tissue in the focal point of the emitted wave pattern and thus recovering the tissue's functionality as is shown in patent publication US 2002/0002345.
Since 1971 extracorporeal shock wave therapy (hereinafter ESWT) has been used successfully and with a low rate of adverse reactions in the field of urology. Despite the relatively high energy flow densities used during ESWT, no major complications (e.g. malignant degeneration of the treated tissue) have been reported.
The German urologist G. Haupt deserves the credit for the acceptance ESWT has gained in the fields of orthopedics and traumatology as well. Urologists have noticed, that larger amounts of energy (i.e. a larger number of pulses) were required to disintegrate calculi in the urethra and bladder than to break down renal calculi. Initially neither the physicists nor the medical scientists involved in these studies had a plausible explanation for this discrepancy. It was while reviewing follow-up x-rays to detect any recurrences of calculi in patients treated for urethral or bladder stones in 1986 that Haupt first noted a thickening of the ala of the ileum, an anatomical structure lying directly in the path of the shock waves aimed at the calculi. This finding was significant since it indicated that a) bone absorbs shock waves and b) shock waves evidently also trigger biological reactions in bone. Haupt subsequently demonstrated the osteoinductive effect of focused shock waves in animal experiments.
Since it is mainly the physical properties of shock waves that play a central role in the use of extracorporeal shock wave therapy for urological applications, basic research on the use of shock waves for orthopedic and traumatological applications also focused primarily on these dynamic mechanical force related type properties.
This mechanistic model attempts to explain the effect of shock waves in tissue by postulating that the shock wave creates micro lesions in the tissue on which it is concentrated without, however, destroying the surrounding soft-tissue and thus triggers repair processes leading to healing.
This model of action was the reason, moreover, that Schaden et al used high numbers of pulses (i.e. up to 12,000 for treatment of the long bones) when employing shock waves for the first time to treat patients with pseudarthrosis. Several of these treatments had to be terminated after only 3,000 to 4,000 pulses for technical reasons, however, it was noted that the treatment resulted in healing of the patients pseudarthroses despite (or perhaps because of) this circumstance. This observation was congruent with the results of the basic research carried out by M. Maier, who demonstrated that the optimal osteoinductive effect of shock waves on rat femora took place at energy flow densities and pulse numbers which caused practically no histological demonstrable tissue destruction. One consequence of this finding was that basic research on shock waves concentrated increasingly on the biological effects of shock waves.
C. J. Wang discovered that a variety of substances displaying high biological activity are released during and after the application of shock waves to tissue. The production of nitric oxygen (NO), vessel endothelial growth factor (VEGF), bone morphogenetic protein (BMP), and other growth factors have been demonstrated. Furthermore, Maier discovered a decline in the number of small-myelinized neurons after shock wave therapy, an observation that could explain the analgesic effect of shock wave therapy. As a consequence of these findings, the mechanistic model was increasingly relegated to a secondary role and supplanted by a microbiological model explaining the action of shock waves.
In practice the use of ESWT has been a results oriented science wherein a clear and accurate understanding of the actual healing process was neither understood nor fully appreciated. As a result a variety of treatments and uses of ESWT in mammals had heretofore never been tried or attempted or if tried, the outcomes were at best mixed.
A primary factor in the reluctance to use ESWT was that the believed threshold energy requirements were so high that the surrounding tissue would hemorrhage, exhibited by hematomas and bleeding around the treated site. This phenomenon is particularly known in the area of focused emitted waves designed for deep penetration into the patient. US patent publication 2005/0010140 recites the disadvantageous effects of cavitation phenomena can be controlled wherein the shock wave source is connected to a control means which controls the release frequency of shock waves as a function of pulse energy in such a manner that higher pulse energy correlates with lower release frequencies of the shock waves and vice versa. The avoidance of cavitation occurrences would it is postulated result in far less pain for the patient.
The present invention recognizes the underlying beneficial attributes of ESWT are not now and may never be fully comprehended, however, under a more advanced molecular theory the authors of the present invention postulated a microbiological model suggesting the response mechanism to such treatment.
This model attempts to explain the effect of ESWT by postulating neovascularization of the treated tissue with simultaneous release of diverse growth factors. The enhanced metabolic activity taking place in the presence of these growth factors could be responsible for the healing of the chronically inflamed tissue while the decrease in afferent nerve fibers causes the analgesic effect.
The present inventors see that ESWT is a highly versatile therapeutic instrument. It can be used as a bioengineering tool to achieve effects such as the production of growth factors or as a surgical instrument to effect an extremely subtle type of denervation. In the field of traumatology, these properties are used primarily to treat fractures with non-union or delayed osseous union. ESWT is also becoming increasingly important for treating the early stages of osteochondritis dissecans.
It is an object therefore of the present invention to provide a shock wave therapy that employs a more effective wave energy transmission, that is both simple to deploy and less target sensitive when compared to reflected focused waves.
It is a further object of the invention to provide a therapeutic treatment of a large target area for surface or subsurface soft tissues such as skin or near skin conditions or diseases including, but not limited to trauma.
There is a need for an apparatus and a process for optimized electro-hydraulic pressure pulse generation by changing the focusing characteristics of a pressure pulse or shock wave so that focused or unfocused wave fronts with nearly plane acoustic wave front, convergent acoustic wave front or divergent acoustic wave front characteristics can be released by the apparatus.
There is also a need for an apparatus for optimized pressure pulse/shock wave generation, wherein waves with defined wave front characteristics, like focused, nearly plane or divergent are released from the apparatus for treating tissues, in particular, for treating skin or skin near conditions including, but not limited to, skin and skin near conditions caused by trauma or diseases.
There is also a need for providing an apparatus that allows treatment without requiring extensive scanning of the area to be treated. This is usually required to cover an area uniformly if apparatuses using a small focal point are used. Such an apparatus would reduce treatment times.
There is a need for an apparatus that produces waves having nearly plane, convergent or divergent acoustic wave front characteristics with adjustably reducible or reduced energy densities compared to wave fronts emitted by focused shock wave generators having a focal point located directly on the treated tissue.
There is also a need for an apparatus and method that allows using existing pressure pulse generating devices to treat tissues which have more area like than volume like characteristics, such as skin.
These and other applications of the present invention are described more fully as follows with first detailed description of shock wave therapeutic methods and then a detailed description of several shock wave devices and apparati for carrying out the methods.